"There will be major deals on all kinds of electronics and back-to-school items," she added.

The annual sale kicked off Monday at 3 p.m. ET and will continue for the next 36 hours.

Amazon's own products will be on sale the entire time, including the new Echo Show, which is being discounted by $100.

The online shopping giant's hands-free camera, known as the Echo Look, is also being discounted by $100.

Great deals from other vendors will come and go during the time.

“There are going to be lightning deals all day long, meaning flash sales on items,” Freeman said. "You have to act quickly if you want to get the best deals.”

The Instant Pot kitchen appliance has been the hottest-selling item the last two years running. Amazon expects it to do well again.

The deals won't just be online as 2018 is the first Prime Day since Amazon purchased the Whole Foods grocery store chain. Thousands of products in the stores will be discounted by 10 percent. If you spend more than $10 at Whole Foods you will get a $10 Amazon gift card to use online during Prime Day.

The deals are only open to Amazon Prime memberships, which cost $120 per year.

Trish Regan, host of "The Intelligence Report" on Fox Business, explained the benefits of having a Prime account.

"I am going to say it is [worth it] if you are going to actually use it — if you are going to use the music, if you are going to use the video, if you are going to order a fair amount of stuff from there than it is probably worth the $120 a year," she said.